What causes Hank distress while giving his statement to the FBI agents in Chapter Eleven?

Hank talks, telling the story he's now come to know so well, and the agents merely sit and listen without interrupting. Hank can't decide whether they believe the events as they've been led to believe and that Hank is merely reiterating the facts or if they already know of his guilt and are just letting him dig himself in deeper and deeper.